CUTADAPT-PE

Trim paired-end reads using cutadapt.

URL: https://github.com/marcelm/cutadapt

Example

This wrapper can be used in the following way:

rule cutadapt:
    input:
        ["reads/{sample}.1.fastq", "reads/{sample}.2.fastq"],
    output:
        fastq1="trimmed/{sample}.1.fastq",
        fastq2="trimmed/{sample}.2.fastq",
        qc="trimmed/{sample}.qc.txt",
    params:
        # https://cutadapt.readthedocs.io/en/stable/guide.html#adapter-types
        adapters="-a AGAGCACACGTCTGAACTCCAGTCAC -g AGATCGGAAGAGCACACGT -A AGAGCACACGTCTGAACTCCAGTCAC -G AGATCGGAAGAGCACACGT",
        # https://cutadapt.readthedocs.io/en/stable/guide.html#
        extra="--minimum-length 1 -q 20",
    log:
        "logs/cutadapt/{sample}.log",
    threads: 4  # set desired number of threads here
    wrapper:
        "v4.6.0/bio/cutadapt/pe"

Note that input, output and log file paths can be chosen freely.

When running with

snakemake --use-conda

the software dependencies will be automatically deployed into an isolated environment before execution.

Notes

• The extra param allows for additional program arguments.

• The adapters param allows for separatelly specifying adapter options (optional).

Software dependencies

• cutadapt=4.9

Input/Output

Input:

• two (paired-end) fastq files

Output:

• two trimmed (paired-end) fastq files

• text file containing trimming statistics

Authors

• Julian de Ruiter

• David Laehnemann

Code

"""Snakemake wrapper for trimming paired-end reads using cutadapt."""

__author__ = "Julian de Ruiter"
__copyright__ = "Copyright 2017, Julian de Ruiter"
__email__ = "julianderuiter@gmail.com"
__license__ = "MIT"


from snakemake.shell import shell


n = len(snakemake.input)
assert n == 2, "Input must contain 2 (paired-end) elements."

extra = snakemake.params.get("extra", "")
adapters = snakemake.params.get("adapters", "")
log = snakemake.log_fmt_shell(stdout=False, stderr=True)

assert (
    extra != "" or adapters != ""
), "No options provided to cutadapt. Please use 'params: adapters=' or 'params: extra='."

shell(
    "cutadapt"
    " --cores {snakemake.threads}"
    " {adapters}"
    " {extra}"
    " -o {snakemake.output.fastq1}"
    " -p {snakemake.output.fastq2}"
    " {snakemake.input}"
    " > {snakemake.output.qc} {log}"
)